How do i stop post back on a button?

If I have a button, how do i suppress postback based on the JavaScript -- like the Page Validators do -- ie: they dont post the page unless there are no javascript erros:





ie:








<asp:button id="button1" runat="server" OnClick="DoThis();" />





<Script Language="JavaScript">





function DoThis(){





if (confirm("Do you want me to Post Back?")==true){


// ok do the post back and whatever!!!


}





}





</Script> ...